Although there have been prior attempts to provide shelf mounting systems utilizing concealed hardware, these systems have had the limitation that the position of the shelf was dictated by the position of the wall studs into which the hardware was screwed or by the position of the anchoring points if conventional screw anchors were employed. Once the hardware was screwed to the wall, the position of the shelf was fixed and the householder could not shift the shelf to other positions, except by removing and reinstalling the hardware at another point on the wall. Furthermore, with existing known prior art systems, the hardware is not completely hidden, the means for retaining the shelf on the supports being visible in the shelf surface. In the case of some of the prior art systems the retaining means consists of small pins or set screws, which are inconvenient to store or use and are easily lost.
Examples of the prior art attempts are shown in Kapnek U.S. Pats. Nos. 3,333,555; 3,527,175; and 3,752,088, U.S. Pat. No. 3,333,555 discloses a fastener which is screwed into a wall stud and has a shaft protruding from the wall which is inserted into a pre-drilled hole in the shelf. The patent shows a pin dropped through a hole in the shelf to engage a lip on the shaft or a set screw engaging the shaft as the means to retain the shelf on the shaft. Both of the means are easily lost, and a set screw near the back of the shelf is awkward to insert, especially if several shelves are to be mounted one above the other. The greatest drawback to the system shown in that patent, however, is that the position of the shelf on the wall is limited to studs aligned with the predrilled holes.
U.S. Pat. No. 3,527,175 also uses a set screw to retain the shelf, although it is spaced in a somewhat more convenient location, further from the back of the shelf. The system disclosed in that patent attempts to solve the problem of adjusting the location of the shelf by fastening the shaft at any desired point on the wall using screw anchors. However, screw anchors are difficult to remove from the wall, should the user desire to move the shelf. Moreover, once the anchors are fastened to the wall, there is no possibility of shifting the position of the shelf along the wall except by removing and repositioning the anchors.
In both U.S. Pat. Nos. 3,333,555 and 3,527,175 the pins or set screws gave rise to noticeable breaks in the continuity of the upper or lower shelf surface.
U.S. Pat. No. 3,752,088 also provides adjustability of location with screw anchors, but the capability of adjustment is subject to the same limitation as the arrangement of U.S. Pat. No. 3,527,175. Friction is relied on for retaining the shelf on its support.